1. Field of the Invention
This invention relates to a system for monitoring an abnormality of oil-filled electric devices such as transformer, reactor, etc., and more particularly it relates to a system for monitoring abnormality in an oil-filled electric device by separating and extracting the gas produced and dissolved in the insulating oil in said device in the event of occurrence of any electrical or thermal abnormality in the case of said device.
2. Description of the Prior Art
It is well known that when an abnormality such as local overheating or partial discharging occurs in a oil-filled electric device such as transformer, rectifier, capacitor, cable, etc., the insulating oil or solid insulated article is decomposed to produce the hydrocarbon type gases such as H.sub.2, CH.sub.4, C.sub.2 H.sub.2, C.sub.2 H.sub.4, C.sub.2 H.sub.6, etc., and/or other types of gas such as CO, CO.sub.2, etc., and most of these gaseous substances stay dissolved in the insulating oil. Therefore, if the gaseous substances dissolved in the insulating oil in a oil-filled electric device are constantly monitored, it is possible to detect abnormality in said device in its early stage.
According to the conventional monitoring systems of this type, internal abnormality of an oil-filled electric device such as transformer is assumptively judged by detecting the concentrations or increments of the various gas components in the oil. To be more specific, according to such conventional monitoring systems, the gas in the insulating oil is separated and collected by a device such as a gas-in-oil separator utilizing Torricelli's vacuum, Toepler pump, piston reciprocation or a gas separating membrane made of an inorganic or organic material provided in the case of the electric device, and the collected gas is measured by gas chromatography or combustible gas sensors to judge presence or absence of abnormality in the device from the total amount of the gas or the absolute amounts of the individual gas components such as H.sub.2, CO, CH.sub.4, C.sub.2 H.sub.4, C.sub.2 H.sub.6, C.sub.3 H.sub.8, etc., or from the degree of increments thereof.
Among the known means for detecting the gas dissolved in the insulating oil in an oil-filled electric device is a system in which the gas dissolved in the insulating oil is separated from said oil and collected in a gas reservoir and then the concentration of the gas in said reservoir is detected by a gas detector, as for instance disclosed in Japanese Laid-Open Patent Application No. 9718/1979 and U.S. Pat. Nos. 4,058,373 and 4,112,737. Since the gas contained in the insulating oil is mostly combustible gas such as hydrocarbon type gas, a commercially available combustible gas detecting element is adaptable as gas detector.
This system is capable of detecting occurrence of abnormality in an oil-filled device from the concentration of the gas collected in the gas reservoir and is also simple in structure. However, it is difficult with this system to detect the components of the gas. In order to detect the gas components by using this system, it is necessary to install the gas detector elements, each having sensitivity to a specific gas alone, that is, having high-degree gas selectivity, in as many number as the gas components to be detected. This is unrealistic.
If the components of the gas separated from the insulating oil can be detected, it becomes possible to assume the type of the abnormality in the oil-filled device, for example, whether such abnormality is occurrence of discharging, local overheating or decomposition of the solid insulated article, and a quite useful device can be provided.
For detecting the gas components in the insulating oil, a system is known in which the insulating oil is sampled into a vessel, then air is blown into the oil to cause bubbling and the gas extracted thereby from the insulating oil is passed through a separating column to separate the gas into the individual components, and then the concentration of each component is detected by a low-selectivity combustible gas detector.
However, as this system is incapable of bubbling the oil in the oil-filled device, it is required to sample out the insulating oil from the device for detecting the gas components. This is very troublesome and uneconomical. It is to be further noted that this type of gas component detecting systems are required to detect the gas components periodically for a prolonged period of time and to also constantly monitor the gas components. Therefore, it is inexpedient for this system to collect the insulating oil from the oil-filled device for every run of detection.
Further, it has been difficult with these conventional systems to know the type of abnormality and the temperature of abnormal heating automatically and in a simple way.